The first official day of spring in March 2026 felt more like summer across much of the southwestern United States, with numerous high-temperature records falling on March 20 amid a bout of extreme heat. Yuma, Arizona reached a record high of 109°F, which is 28 degrees above the 1991-2020 climatological normal for that date. Four other locations—near Yuma and Martinez Lake in Arizona and Ogilby and Winterhaven in California—tied for the highest temperatures in the U.S. on March 20, 2026, reaching 112°F, smashing the record for the hottest March day in the continental U.S. by 4 degrees.
A map shows air temperatures on the afternoon of March 20, 2026, modeled at 2 meters above the ground using the GEOS model, with the darkest reds indicating temperatures reaching or exceeding 104 degrees Fahrenheit. Measurements from weather stations on March 20 pinpointed some of the highest U.S. temperatures in Arizona and California. The historic heat across the Southwest has set new daily temperature records in at least 30 cities in California, Oregon, Idaho, Nevada, Arizona, Wyoming, Colorado, and New Mexico. Several other U.S. states saw temperatures soar in late March 2026, including Texas where Lubbock experienced several days in the mid to upper 90s. Sweltering temperatures extended into Mexico in late March 2026, where a new March record was set in Hermosillo, Mexico, with temperatures reaching 108°F.
The heat was driven by a persistent high-pressure system, which the NWS noted was similar in strength to conditions seen in summer. The high-pressure system remained over the region for more than a week, keeping the air dry and skies clear across a vast stretch of the U.S. and Mexico, and the heat was expected to spread east into the U.S. Midwest and Southeast by the following week. A gigantic heat dome that baked the Southwest is creeping eastward and may be one of the most expansive heat waves in American history.
This early-season heat is unprecedented, with Phoenix never hitting 100 degrees before March 26 in 137 years of record-keeping. March 2024 was the hottest March on record for the U.S., with an average temperature 5.19°C above the 20th-century normal, making it the most abnormally hot month in 132 years of records. More than 19,800 daily temperature records were broken for heat across the country in March. Temperatures at or above 100 degrees Fahrenheit were forecast in the Southwest on Saturday, with Yuma Desert reaching 112 degrees on Friday, a record for the highest March temperature in the U.S.
Snow surveys across the American West show record-low snowpack levels after a historically warm winter and searing March temperatures. Snow water equivalent in California's Sierra Nevada was 4.9 inches (18% of average) as of Monday ahead of the April 1 survey. Snow water equivalent in the Colorado River headwaters was just over 4 inches (24% of average) on Monday, less than half the previous record low. The Great Basin had 16% of average SWE, the lower Colorado region 10%, and the Rio Grande 8% on Monday.
Extreme heat is creating 'non-survivable' conditions for humans in heatwaves, with older people particularly susceptible. Heatwaves in Mecca (2024), Bangkok (2024), Phoenix (2023), Mount Isa (2019), Larkana (2015), and Seville (2003) had thousands of deaths despite not approaching the wet bulb limit of 35°C. The Larkana and Phoenix heatwaves included periods not survivable for older people even in shade.
Shoreline stations in California have recorded record-breaking daily high water temperatures, with La Jolla station registering temperatures 10°F above historical average last month. A marine heatwave in southern California, caused by a high-pressure atmospheric system, is drawing comparisons to 'the Blob' from a decade ago. March 2024 was the second warmest month ever measured in the sea, with an average sea temperature of nearly 21 degrees. A new study found marine heat waves supercharge damage caused by hurricanes and tropical cyclones, leading to 60% more disasters causing at least $1 billion in damage.
Temperatures could reach 107 degrees in Phoenix, Arizona, and 90-degree heat in Los Angeles due to a heat dome. 23 states are expected to fall under the massive heat dome spreading into the Central U.S. on Friday and Saturday. April, May, and June are likely to be hotter than normal almost everywhere in the U.S. Some forecasts see 98°F in Phoenix on Tuesday, followed by 103, 105 and two days of 107. It has already started in Los Angeles, with unusual 90-degree March weather that had people in shorts and tank tops seeking shade wherever they could find it.
Americans in every state have been warned to brace for extreme weather, including deadly heat in the Southwest and a polar vortex in the Midwest and East. Two storms will dump snow by the foot over northern Great Lakes states. The dreaded polar vortex will again invade the Midwest and East with soul-crushing Arctic chill. Around the same time as the heat starts blasting Phoenix, the polar vortex is forecast to send its chill deep into the Midwest and East, even bordering some of the Southeast. Minneapolis will hover around zero for a low, and Chicago will be in the single digits Tuesday, with temperatures in the teens and 20s in the Northeast and 20s in the Mid-Atlantic the next day, and Atlanta could drop to the 20s.
Weather whiplash has already hit much of the East, with Washington, D.C., residents walking around in shorts in record-breaking 86 degrees Fahrenheit on Wednesday and it snowing on Thursday. Parts of Oklahoma, Nebraska, northern Texas, and South Dakota are registering highs at least 20 degrees Fahrenheit above their March averages. Nearly every part of the United States is getting walloped by wild weather or just about to be.
International climate scientists at World Weather Attribution state this record-shattering heat would be 'virtually impossible' without the effects of climate change. Scientists fear the El Niño phenomenon is returning, which could lead to even higher global temperatures and more extreme weather. The Southwest will soon bake with day after day of record 100-degree-plus heat. A heat dome will form early next week and park over the Southwest, baking temperatures to triple digits that haven’t been seen this early in the year.
Authorities have not detailed specific measures being taken to protect vulnerable populations from the extreme heat, leaving uncertainty about preparedness efforts. The record-low snowpack levels raise concerns about water supply and agriculture in the affected regions, though the full impact remains unclear. The projected economic cost of the extreme weather events across the U.S. has not been estimated, adding to the unknowns surrounding this crisis.
The snowpack crisis could severely impact water supply for millions in the West, but long-term adaptation strategies to address these increasingly frequent extreme weather events are still under consideration. Confirmed fatalities directly attributed to the March 2026 heatwave have not been reported, highlighting the ongoing risks as temperatures soar. Broader implications for infrastructure, energy demand, and public health systems remain to be fully assessed as the heatwave expands.